Priority is claimed to Korean Patent Application No. 10-2004-0006948, filed on Feb. 3, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an image display apparatus in which two-dimensional (2D) and three-dimensional (3D) images can be selectively displayed, and more particularly to a 2D and 3D image display apparatus having the same and a method of manufacturing the light transmission controlling apparatus.
2. Description of the Related Art
In general, a 3D image can be implemented using a viewer's binocular disparity. As the 3D image implementing method using the binocular disparity, there are a method where a viewer wears glasses for displaying the 3D image such as polarization glasses and liquid crystal (LC) shutter glasses, and a method where the viewer observes in his/her naked eyes using a unit having a lenticular lens, a barallax barrier, a barallax illumination and the like. The former is called “stereoscopy method” and the latter is called “autostereoscopy method”.
The stereoscopy method is applied to a place where several persons can view the image using a polarization projector, such as a theater. The autostereoscopy method is applied to a game display, a home television set, an exhibition display and the like, which are used by a single person or a small number of people.
Current study is concentrated on the implementing the 3D image using the autostereoscopy method, and several products relating to this are on sale.
3D-image display devices, which are being currently introduced, can implement only a 3D image, and are at a higher price than a 2D-image display device.
However, since 3D image contents are not widely available in large quantity, the high-priced 3D-image display devices cannot satisfy customers' interest.
Accordingly, as recent studies are being made on methods for manufacturing a display device for selectively implementing both 2D and 3D images, various products are being introduced.
Among the recently introduced products, there is a display for selectively displaying the 2D and 3D images using a liquid crystal shutter provided at a rear of a Thin Film Transistor Liquid Crystal Display (TFT-LCD). The display has an excellent 2D/3D-image variable characteristic. However, due to a thickness of the liquid crystal shutter, the display is increased in thickness. Further, since the display uses a polarizer film, it is difficult to achieve light efficiency as desired.
FIG. 1 illustrates a conventional 3D-image exclusive display apparatus employing a parallax illumination way.
Referring to FIG. 1, the conventional 3D-image exclusive display includes a general Liquid Crystal Display (LCD) 10 for displaying an image thereon, and a slit plate 14 installed at a rear of the general LCD 10. The slit plate 14 is spaced apart from the LCD 10 by a predetermined distance (dS). A plurality of slits 16 are provided on a surface of the slit plate 14 facing with the LCD 10. Light incident on the slit plate 14 is incident on the LCD 10 through the slits 16. Accordingly, the slits 16 are a line source for the LCD 10. In FIG. 1, reference numeral 12 represents a pixel of the LCD 10.
The 3D-image exclusive display apparatus shown in FIG. 1 has an advantage in that a structure is simple, and luminance is not only excellent, but also Moire interference is apparent in comparison to the display apparatus employing a parallax barrier way.
However, since the 3D-image exclusive display apparatus shown in FIG. 1 employs a fixed 3D display using a fixed slit plate, the viewer can view only the 3D image in which left and right images are separated. For all that, as described above, since the 3D contents are not widely distributed in large amounts at present, and it is expected that the 2D and 3D contents coexist if only in the future for the present, it will not easy for a customer to willingly purchase the high-priced 3D-image exclusive display apparatus.
Accordingly, a display apparatus for selectively displaying the 2D image and the 3D image (Hereinafter, referred to as “2D/3D display apparatus”) is required.
FIG. 2 illustrates a conventional 2D/3D display apparatus being currently popularized. In FIG. 2, a reference numeral A1 denotes a liquid crystal panel for displaying the image thereon using a thin film transistor as a switch element.
Referring to FIG. 2, a liquid crystal shutter A2 is provided at a rear of the liquid crystal panel A1, and a light source A3 is provided at a rear of the liquid crystal shutter A2. The light source A3 is a backlight used for the general LCD. An operation principle of the liquid crystal shutter A2 is identical with that of the liquid crystal panel A1. Accordingly, an electric signal applied to the liquid crystal shutter A2 is controlled to allow a specific region of the liquid crystal shutter A2 to function as a transmission region through which an incident light from the light source A3 passes, or to function as a screen region by which the incident light is screened. Further, the electric signal applied to the liquid crystal shutter A2 is controlled to allow a region of the liquid crystal shutter A2 corresponding to the slit 16 of the display apparatus shown in FIG. 1 to function as the transmission region, and to allow a remaining region of the liquid crystal shutter A2 to function as the screen region. In case that the liquid crystal shutter A2 is driven as above, the 2D/3D display apparatus shown in FIG. 2 becomes identical with the 3D image exclusive display apparatus shown in FIG. 1.
In the meanwhile, the electric signal applied to the liquid crystal shutter A2 is controlled to allow an entire region of the liquid crystal shutter A2 to function as the transmission region. In this case, the 2D/3D display apparatus shown in FIG. 2 becomes essentially identical with a 2D image display apparatus.
As such, the conventional 2D/3D display apparatus shown in FIG. 2 has an advantage in that since the liquid crystal shutter A2 can be used to selectively implement a 2D-image exclusive light source and a 3D-image exclusive light source, the 2D or 3D image can be selectively embodied.
However, the 2D/3D display apparatus shown in FIG. 2 has disadvantages in that the display apparatus can be increased in thickness and its manufacture cost can be also increased due to the liquid crystal shutter A2 provided between the liquid crystal panel A1 for displaying the image thereon and the light source A3, and further the light efficiency is reduced due to the necessity of inserting an additional polarizer film.
An observation distance (L) necessary for observing the 3D image is given in the following Equation 1.L=(d×E)/p  [Equation 1]
In the Equation 1, “L” represents a distance from the liquid crystal panel A1 to viewer's eyes 26L and 26R, and “d” represents a distance from the liquid crystal shutter A2 to the front surface of the liquid crystal panel A1. Additionally, “E” represents a distance between viewer's left eye 26L and right eye 26R, and “p” represents a pixel pitch of the liquid crystal panel A1.
Generally, the pixel pitch (p) of the liquid crystal panel A1 is about 110 μm, and the distance (E) between both eyes 26L and 26R is about 65 mm. Additionally, considering that a rear glass plate of the liquid crystal panel A1 has a thickness of about 0.7 mm, a polarizer has a thickness of 0.2 mm, and the glass plate of the liquid crystal shutter A2 has the thickness of 0.7 mm, the distance (d) is calculated as 1.6 mm. This distance (d) should be converted into air thickness since the image reaches the viewer through air. For this, the distance 1.6 mm is divided by 1.52. If these values are applied to the Equation 1, the observation distance (L) necessary for observing the 3D image is about 622 mm {(((0.7 mm+0.2 mm+0.7 mm)/1.52)*65 mm)/0.11 mm}.
Referring to FIG. 3, the liquid crystal panel A1 includes a first polarizer 50, a first transparent substrate 52, a first Indium-Tin-Oxide (ITO) electrode 54 connected to the TFT, a first liquid crystal layer 55, a second ITO electrode 58 used as a common electrode, a second transparent substrate 60 and a 135° polarizer 62, which are arrayed in a sequence. Additionally, the liquid crystal shutter A2 includes a third transparent substrate 70, a third ITO electrode 72 connected to the TFT, a liquid crystal layer 74, a fourth ITO electrode 76 used as a common electrode, a fourth transparent substrate 78 and a second polarizer 80, which are arrayed in a sequence from the liquid crystal panel A1 toward a light source A3. When the liquid crystal shutter A2 is in an on state, the incident light from the light source A3, that is, the backlight passes through the liquid crystal shutter A2 as it is, and when the liquid crystal shutter A2 is in an off state, a polarization direction of the incident light is rotated by 90°.
Considering the case that a personal LCD monitor is used as the 2D/3D display apparatus, the observation distance (L) is a long distance if the user is observing with hands placed on a keyboard. Further, it would be advantageous if the observation distance (L) were smaller in instances that the 2D/3D display apparatus is applied to a personal mobile terminal such as a hand phone and a Portable Digital Assistant (PDA). Accordingly, in this aspect, it is difficult that the 2D/3D display apparatus shown in FIG. 2 is applied to the personal LCD monitor or the personal mobile terminal. Naturally, this drawback can be solved by overcoming a difficulty in the manufacturing process to permit the use of a heavy thin glass plate or a polymer substrate. However, since the liquid crystal shutter A2 of the 2D/3D display apparatus shown in FIG. 2 necessarily requires a polarizer film, it is difficult to achieve the desired light efficiency.
In the meanwhile, reference numerals L and R of FIG. 2 represents pixels of the liquid crystal panel A1. An image of a slit light source 22a seen through the pixel (L) is incident only on the viewer's left eye 26L, and the image of the slit light source 22a seen through the pixel (R) is incident only on the viewer's right eye 26R. Accordingly, disparity is generated and the viewer views the 3D image.
As the observation distance and the light efficiency for the 3D image become important factors, various 2D/3D display apparatuses are introduced for improving them. FIG. 4 illustrates one example.
The 2D/3D display apparatus shown in FIG. 4 sequentially includes a patterned retarder A5 which is called a phase difference plate and a liquid crystal shutter A4 between the liquid crystal panel A1 for displaying the image thereon and the light source A3 for the purpose of shortening the observation distance. Arrows in the retarder A5 denotes a fast axis.
When the polarization axis of the incident light incident on the retarder A5 is parallel with or is vertical to the fast axis of the retarder A5, the incident light passes through the retarder A5 as it is. However, when the polarization axis of the incident light is angled by 45° with respect to the fast axis, the polarization axis of the incident light is rotated by 90° due to the retarder A5. The parts of the retarder A5, which are divided in a slit form, have the fast axes angled by 45° with one another.
The liquid crystal shutter A4 includes a fifth transparent substrate 90, a fifth ITO electrode 92, a third liquid crystal layer 94, a sixth ITO electrode 96, a sixth transparent substrate 98 and a third polarizer 100, which are arrayed in a sequence from the retarder A5 toward the light source A3. The fifth and sixth ITO electrodes 92 and 96, which are not patterned, are in contact with a front surface of the third liquid crystal layer 94. When the liquid crystal shutter A4 is in an on state, the incident light on the liquid crystal shutter A4 passes through the liquid crystal shutter A4. To the contrary, when the liquid crystal shutter A4 is in an off state, the polarization axis of the incident light is rotated by 45 degrees.
Accordingly, when the liquid crystal shutter A4 is in the on state, there is no light with the polarization axis vertical to the 135° polarizer 62 of the liquid crystal panel A1, that is, the polarization axis of 45° among light passing through the retarder A5. This means that light is incident on the entire surface of the liquid crystal panel A1. Accordingly, the viewer can view the 2D image.
On the contrary, when the liquid crystal shutter A4 is in the off state, the polarization axis of the incident light on the liquid crystal shutter A4 is rotated by 45 degrees. Therefore, light with the polarization axis vertical to the 135° polarizer 62 of the liquid crystal panel A1 among light passing through the retarder A5 becomes a slit form which are spaced apart at a predetermined interval. This means that the incident light on the 135° polarizer 62 of the liquid crystal panel A1 is light separated in the slit form. Accordingly, the viewer can view the 3D image.
The conventional 2D/3D display apparatus uses the liquid crystal shutter having the same construction as the liquid crystal panel. Therefore, the conventional 2D/3D display apparatus is the same as a display apparatus that two liquid crystal panels are practically used. Accordingly, the conventional 2D/3D display apparatus is increased in thickness and power consumption. Further, a light generating part for 2D/3D image of the conventional 2D/3D display apparatus has the polarizer film. Accordingly, the light efficiency of the conventional 2D/3D display apparatus is reduced. Furthermore, the refractive indexes are different from one another when red (R), green (G) and blue (B), which are used to display a colorful image, pass through the retarder A5. Accordingly, color dispersion can be observed in the conventional 2D/3D display apparatus.